Optical measuring and monitoring applications generally require a window from the detection apparatus to the measurement/monitoring target. In addition, optical monitoring/measuring requires sufficient lighting to function properly. Particularly in process environments, the window and light source are susceptible to becoming obscured when dust, moisture, and other contaminants collect on the window and light the surface of the source. A dirty window or light source, for example, can gradually affect the measurement/monitoring results and, ultimately, block the view and light with respect to the measurement/monitoring target. Thus, optical measuring/monitoring devices and systems require periodic manual cleaning, which is expensive and, in some cases, difficult or impossible to arrange.
Tissue manufacturing machines utilized in optical/monitoring applications, for example, present some unique challenges with respect to maintaining a clear sharp picture and optimal lighting due to the amount of fiber dust generated by the machine in normal operation. A number of approaches to solve this problem currently exist, including wiper blades, moving windows, air knives, pinholes or water sprays, or combinations of methods to clear the window and light source of debris.
Each of the aforementioned methods has distinct drawbacks. For example, a disadvantage of wiper blades and water sprays is that such components can block a user's view for a short period of time, thus preventing proper measurement/monitoring. Additionally, a washing system that utilizes water can exacerbate the situation by transforming the fiber dust into a paste that can then accumulate, and eventually require extensive cleaning. Moving windows (e.g. rotating window) utilize multiple moving parts, which require periodic maintenance. A pinhole, utilized in the context of tissue manufacturing machines, is typically configured as a small hole without a window, which requires highly specific and costly pinhole optics. Additionally, air knives typically generate turbulent airflow, which does not fully protect the window from particulate accumulation.
The standard air knife can be successful in keeping a majority of the dust away from the lens or window, but due to static charge build-up on the glass and dead area under the wipe, eventually dust does build up and obscures the view. Therefore, it is believed that a need exists for a highly effective system and method to periodically clear debris from a window or light source with minimal interference or downtime.